Two kinds of arguments have been deployed against SSM. The first, which have more to do with giving voice to the identity of SSM opponents than winning the debate according to norms of technocratic rhetoric, are (in the broadest sense of the term) theological. They use the “definition of marriage,” its existence as a “pre-political form of relationship,” and even (surreptitiously connecting theological presuppositions to real world concerns) the idea that marriage loses its “pull” if it isn’t swaddled in all of its traditional (theological) trappings. Giving voice to a political group’s identity doesn’t only serve internal therapeutic, self-disciplining and self-motivating functions. if the identity is attractive enough it could well draw many whose present political identities are, at least, compatible with the newly articulated one into its corner. It is possible that identity-politics are more persuasive than more rational modes.
The second kind of argument follows the norms of technocratic rhetoric. Technocrats call it “public reason” but this is just myopia or self-flattery. Myopia if it is meant as a descriptive claim. That is, if the idea is that policies actually win or lose on the basis of the weight of “public reason” then public reason must include, beyond technocratic argumentation, the sorts of a-rational considerations at the heart of first amendment law, drug laws, and immigration laws [to name but a few]. Self-flattery if it is meant to stand as a normative ideal; technocratic rhetoric, tied, as it is, to conventional wisdom is massively unprincipled, particularly when it comes to baselines and burdens of proof.
Though they deal in the norms of technocratic rhetoric, there is no reason reason to think technocrats – judges, politically-minded lawyers, wonks – exempt from a-rational forms of persuasion. Nonetheless, a fundamental aspect of the technocratic identity is that it be able to deploy technocratic rhetoric in defense of its commitments. Thus opponents of SSM also developed, in addition to their theology, technocratic arguments against SSM: harmful to children because they’d be raised differently or teased [cite to an FRC white paper], risky for the institution of marriage in the same way that any social upheaval might be, a reckless exercise in social engineering [cite to Hayek, cite to Burke], etc. Technocratic argumentation is characterized (a) by appeals to a less capacious set of harms (pain, lost opportunity) than those to which various theological arguments can appeal (spiritual losses, a vanishing tradition, the destruction of a concept) and (b) the sober presentation of, preferably (though not necessarily) data driven, causal explanations of how that harm would eventuate.
If it is correct that identity-politics is more persuasive than the more rational modes of political rhetoric, it is still the case that technocrats – who, for the most part, actually craft policy – have at least a felt-need to rationalize their decisions in the language of technocracy. Jonathon Turley, in his op-ed on polygamy previously mentioned, makes a first effort along these lines:
Others have opposed polygamy on the grounds that, while the Browns believe in the right of women to divorce or leave such unions, some polygamous families involve the abuse or domination of women. Of course, the government should prosecute abuse wherever it is found. But there is nothing uniquely abusive about consenting polygamous relationships. It is no more fair to prosecute the Browns because of abuse in other polygamous families than it would be to hold a conventional family liable for the hundreds of thousands of domestic violence cases each year in monogamous families.
A prediction: if polygamy ever becomes a hot-button issue, this subproblem – polygamy and the domination of women – will be a technocratic flashpoint. It will also play a role in identity-politics, where domination will be defined capaciously by anti-polygamists to include ineffable family dynamics, and narrowly by pro-polygamists (as by Turley) to include only “[physical] abuse.” But it will be most visible on the technocratic field of play. The anti-polygamy side will give evidence and argumentation tending to show that polygamous women are less well-educated, and more home bound, than their non-polygamous counterparts [according to whatever baseline makes the claim come out right]; that there is great violence against polygamous women [evading the comparison to monogamous families by relying on the strong burden of proof those who would show that monogamous relationships also have problematic levels of violence have to overcome]; and that the children of polygamous families are marginalized. The pro-polygamy side will develop a similar matrix of arguments, presupposing different baselines and burdens. The winner at the theological level will slap on a coat of his side’s technocratic paint, and the show will move along.